1. Field of the Invention
The present invention relates to orthopedic surgical instruments, such as surgical guides, surgical cutting instruments, and the like that are used to remove a predetermined amount of the patient's patella so that the patella can receive a prosthesis as part of knee joint replacement surgery. Even more particularly, the present invention relates to an improved patella clamp apparatus that will allow the user to center the cut (eg. a reamer cut) on the patella vertical ridge by providing a reamer collet that can be offset with respect to a patella holding jaw that cradles the patella during cutting.
2. General Background
In total knee arthroplasty, the patella usually requires a new articular surface. This new surface can be obtained using an implant designed to conform to the geometry of the mating femoral implant. It is important that the patella position and tracking be reproduced with the implants. Thus, the instrument must be easy to use and yield reproducible results.
There are primarily two types of patella implants. One type requires a resurfacing of the patella. The other type requires that an inset or cavity be prepared for receiving the implant. With the resurfacing patella implant, the patella requires a flat plane for placement of the implant thereon. This plane is typically obtained by using a sawing or a reaming technique.
A second type of implant is the inset patella implant. The inset patella implant requires an inset surface in the patella to place the implant. This surface can only be obtained by a reaming type instrument.
There are a number of issued patents that are concerned with patella clamps in general. These prior art patella clamp instruments provide the user with either a reamer-type cutting apparatus or a saw-type cutting apparatus.
A recently issued patent, entitled "Method For Implanting A Patellar Prosthesis", is issued to W. E. Mikhail, U.S. Pat. No. 5,180,384. The Mikhail patent discloses a method for preparing a patella for receiving a patellar implant and for implanting a prosthesis therein. An elongated passageway is formed in the patella which is then reamed to form a cavity of a size and configuration to receive the patella prosthesis using a cannulated reamer telescoped over a guide rod positioned in the elongated passageway.
The Whitlock et al. U.S. Pat. No. 5,147,365 discloses a patella osteotomy guide comprising a plier-like appliance with curved jaws for grasping a patient's patella. A row of teeth faces inwardly from the jaws. The teeth are generally of pyramid shape, but a vertex of each tooth lies in a plane containing a bottom side of the respective jaw. Each of the jaws has an integral saw capture slot and the tips of the jaws are extended. A rotating, calibrated stylus measures the position of the patella with respect to the integral saw capture slots. The rotating stylus also functions as a pivot or fulcrum about which the jaws and handles of the osteotomy guide rotate. Handles for the osteotomy guide are offset from the plane of the jaws. The rotating stylus can be displaced up and down and then locked into a selected position using a draw bar and captured balls. A bowed retaining ring imparts a certain amount of pre-load to the stylus and draw bar assembly to hold the assembly in a selected position.
A patella cutting clamp is disclosed in U.S. Pat. No. 5,108,401 issued to Insall et al. The Insall device discloses a patella cutting clamp that comprises a pair of jaw members joined together in scissors-like relation for pivotal movement relative to each other about a pivot axis intermediate their ends. Each jaw member has a handle portion extending in one direction from the pivot axis and a jaw portion extending in the other direction. The jaw portions have edges facing each other that are shaped for engagement with opposite borders of a patella. Teeth along the patella-gripping edges grip and hold the patella firmly. Saw guide slots in the jaw portions lying in a common plane guide the saw when the saw cut is made. A patella elevator member is attached to the jaw members for movement along the pivot axis and has a platform portion adapted to engage the anterior aspect of the patella. A mechanism is provided for establishing and maintaining a predetermined position of the elevator member relative to the jaw members and thereby positioning the patella at a predetermined position relative to the saw guide slots. Another mechanism holds the jaw members in an adjusted position relative to each other with the jaw portions engaging and holding the patella.
U.S. Pat. No. 5,129,908 issued to Thomas Petersen and entitled "Method And Instruments For Resection Of The Patella" discloses a method of performing surgery to resect the patella for purpose of installing a patellar prosthesis, along with instruments used in such surgery. The instruments include a combined clamping device and reaming guide which when clamped about the patella provides a guide for reaming the surface thereof as well as a limit stop device designed to prevent reaming the patella too deeply. The instruments also include a reaming device designed to ream an annulus of material from the patella, leaving a central raised portion for fixation of a patellar prosthesis.
A patellar clamp and reamer with an adjustable stop is disclosed in the Heldreth U.S. Pat. No. 5,129,907. The '907 patent discloses a patellar clamp and reamer for performing either a total surfacing procedure or insetting procedure for preparing the patellar surface for a prosthetic implant, including an adjustable stop connected to the clamp and engaging a collar on the reamer shaft to space the reamer blade a calibrated distance from the clamp's reference jaw. The stop is calibrated and includes indicator thereon in terms of the thickness of patellar bone to remain after resection.
The Burkinshaw et al. U.S. Pat. No. 5,021,055 discloses a patellar clamp and surgical saw guide for preparing a patella to receive a prosthetic articulating surface on the patella's posterior side. A guide plate supports a saw block. The guide plate can be swiveled so that a sagittal saw can be presented to the patella from any desired angle. The saw block can be advanced or retracted axially so that more or less of the patella will be cut away by the sagittal saw. A scale enables the location of the proposed cut to be quickly and accurately determined. Storage apparatus in a handle of the clamp holds different specialized tools for use during surgery.
A patella clamp is disclosed in the Petersen U.S. Pat. No. 4,706,660 which includes a fixed jaw having a spike centrally disposed on a part spherical surface with this spike being axially aligned with a reciprocating plunger. The plunger is operated by a second handle pivotally disposed with respect to the first handle and spring biasing means between the handles biases them in a direction of separation of the plunger and spike.
Another Petersen U.S. Pat. 4,633,862 entitled "Patellar Resection Sawguide" discloses a method and instruments for the installation of a patellar button prosthesis. The first instrument consists of a saw guide including gauges integrally attached thereto which aid the surgeon in determining whether the patella has been grasped at the correct location with respect to the anterior and posterior sides thereof, which determine for the surgeon whether adequate bone stock will remain after resection of the patella, and which are chosen to correspond with the particular thickness of the patellar button which is to be installed. The second instrument consists of a drill guide including structure enabling its attachment to one of the jaws of the saw guide so that the saw guide may be retained in position about the patella after resection. A further instrument usable with the present invention consist of a drill bit including a collar which is provided to interact with holes formed in the drill guide to as to limit the depth of the holes which are drilled in the patella for the purpose of installation of the patellar button. Finally, a patella clamp is provided which includes a single moveable jaw limited in its movement solely to reciprocation, which clamp is utilized to install the patellar button onto the resected patella. The disclosed method involves the use of the above described instruments for the purpose of installation of a patellar button prosthesis.
The Shapiro U.S. Pat. No. 4,565,192 discloses a device for cutting a portion of a patella during knee surgery in which the articular surface of the patella along with a portion of the bone of the patella is cut away for implantation of a prosthesis. The device disclosed provides a fixed clamping member and an adjustable clamping member which clamp the patella and space from the patella a support surface for an oscillating saw used in the cutting of the patella. The precise plane of cut is provided by the use of a placement aid which is used according to the method of the present invention. The placement aid positions the support surface a precise depth below the articular surface of the patella during the clamping procedure, which clamping procedure also horizontally levels the support surface and the device so that all cuts through the patella are made in a perfectly horizontal place. Spacers are also provided which are mountable over the support surface and are used to allow for progressively deeper cuts to be made in the patella through parallel horizontal planes of cut by allowing interchanges of one spacer for another of less thickness. Each spacer has its own flat surface that allows support of the oscillating saw thereon for cutting through the patella during that particular cut as defined by the thickness of the spacer used.